1. Field of the Invention
The present invention relates to a turret type tool post for lathes and, more specifically, to a turret type tool post which is so constructed that a turret and rotating tools mounted on the turret are driven by a common drive motor.
2. Description of the Prior Art
For implementation of a plurality of types of machining such as facing and drilling on a workpiece, there has conventionally been used a combined-machining lathe capable of performing a plurality of types of machining with one-time chucking in terms of machining efficiency. As a turret type tool post disposable in such combined-machining lathes, there is known, for example, a turret type tool post disclosed in examined Japanese Patent Publication No. 58-33043 (unexamined Japanese Patent Publication No. 55-157407).
In this turret type tool post, both its tool-spindle-rotation drive mechanism section and a turret-indexing drive mechanism section are driven by one drive motor. For this purpose, clutches for transmitting/interrupting driving force of the drive motor to the tool-spindle-rotation drive mechanism section and the turret-indexing drive mechanism section are provided for the tool-spindle-rotation drive mechanism section and the turret-indexing drive mechanism section, respectively.
The clutches, to which a tool-spindle clutch lever and a turret clutch lever are connected, respectively, are driven by these tool-spindle clutch lever and turret clutch lever, respectively. The tool-spindle clutch lever and the turret clutch lever are driven by clutch control rods coupled to driving cylinders, respectively. Thus, the tool-spindle clutch lever and the turret clutch lever are driven by the clutch control rods, respectively, which are driven by the driving cylinders, and further the clutches are driven by the tool-spindle clutch lever and the turret clutch lever, by which transmission and interruption of rotational power is fulfilled.
Also, a turret clamping lever for clamping/unclamping the turret is provided so as to be driven by the clutch control rod, as the tool-spindle clutch lever and the turret clutch lever are. The turret is switched between non-rotating state and rotating state by operation of this turret clamping lever.
However, because of its constitution that each of the tool-spindle-rotation drive mechanism section and the turret-indexing drive mechanism section is equipped with a clutch and a clutch lever so that the tool-spindle-rotation drive mechanism section and the turret-indexing drive mechanism section can be driven by one drive motor, the conventional turret device has been complex in rotational-power transmission structure, thus having limitations on downsizing of the device. Further, the structure that the clutch is driven by the clutch lever results in poor transmission efficiency of its driving force, which leads to poorer switching responsivity or possible occurrence of malfunction.
Furthermore, since the clutch lever is normally engaged with each of the clutches that rotate with the drive motor, there is another problem that heat generation or noise is likely to occur to the place of their engagement. This problem largely matters particularly to the tool-spindle-rotation drive mechanism section, which rotates the tool at high-speed.
The present invention having been accomplished in view of these and other problems, an object of the present invention is to provide a turret type tool post which is simple in rotational-power switching and transmitting structure and yet capable of size reduction.
In order to achieve the above object, according to the present invention, there is provided a turret type tool post comprising: at least one of a tool holder for holding a tool rotatably, the tool holder have a rotating shaft for rotating the tool; a turret for holding the tool holder removably; a tool post body for holding the turret rotatably; an indexing drive mechanism for rotating the turret to index a tool holder which has been mounted on the turret to a machining position; a tool rotation drive mechanism for rotating the rotating shaft of the tool holder indexed to the machining position; a drive motor; a first drive shaft which is to be engaged with an output shaft of the drive motor so as to be rotated by rotational power of the drive motor; and a power transmission switching mechanisms which is to be engaged with the first drive shaft so as to transmit rotational power of the first drive shaft selectively to either the tool rotation drive mechanism or the indexing drive mechanism, wherein
the tool rotation drive mechanism includes a second drive shaft disposed coaxial with the first drive shaft;
the indexing drive mechanism includes a third drive shaft having a gear and disposed so as to be spaced at a certain distance from and parallel to the first and second drive shafts;
the power transmission switching mechanism includes a cylinder formed in the tool post body, a hollow piston which is to be inserted into the cylinder and which is movable in an axial direction of the first and second drive shafts, and a hollow switching shaft which is rotatably held within the piston and which has a gear at an outer peripheral portion outside the piston, and wherein
the switching shaft is so arranged that the first drive shaft is to be inserted into a hollow portion of the switching shaft, allowing the switching shaft in engagement with the first drive shaft to be rotated integrally along with the first drive shaft, and that when the switching shaft moves in the axial direction along with the piston to one side of the axial direction, the gear of the switching shaft goes out of mating with the gear of the third drive shaft and the second drive shaft is inserted into the hollow portion, allowing the switching shaft in engagement with the second drive shaft to transmit rotational power of the first drive shaft to the second drive shaft, and when the switching shaft moves to the other side of the axial direction, the second drive shaft is withdrawn from the hollow portion so that the switching shaft is disengaged therefrom while the gear of the switching shaft is mated with the gear of the third drive shaft, allowing the switching shaft to transmit rotational power of the first drive shaft to the third drive shaft.
In this turret type tool post, when the piston inserted into the cylinder is moved to the one side by working fluid such as pressure oil, the switching shaft is moved to the one side along with the piston so that its gear goes out of mating with the gear of the third drive shaft while having the second drive shaft inserted into its hollow portion in engagement with this second drive shaft, thus making it possible to transmit rotational power of the first drive shaft to the second drive shaft via the switching shaft. As a result, rotational power of the drive motor is transferred to the tool rotation drive mechanism via the first drive shaft and the switching shaft, and the tool held on the tool holder is rotated and driven by the tool rotation drive mechanism.
On the other hand, when the piston is moved to the other side by the working fluid, the second drive shaft is withdrawn from the hollow portion of the switching shaft so that these second drive shaft and switching shaft are disengaged from each other while the gear of the switching shaft is mated with the gear of the third drive shaft, thus making it possible to transmit rotational power of the first drive shaft to the third drive shaft. As a result, rotational power of the drive motor is transferred to the indexing drive mechanism via the first drive shaft and the switching shaft, and the turret is rotated by the indexing drive mechanism, so that a desired tool holder is indexed to the machining position.
The engagement between the first drive shaft, the switching shaft and the second drive shaft can be fulfilled by a combination of spline shaft and spline hole as an example.
As shown above, in this turret type tool post, either the second drive shaft or the third drive shaft can selectively and switchably be connected to the first drive shaft by moving the switching shaft held within the piston in a direction along the axis of the first and second drive shafts, which are disposed coaxial with each other, by operation of the piston. As a result, rotational power of the drive motor can be transferred switchably either to the second drive shaft or the third drive shaft. Accordingly, as compared with power transmission switching mechanisms involving the use of clutch and clutch lever as in the prior art, the mechanism can be simplified in structure and yet reduced in size.
Also, the switching shaft, which is driven by the piston that holds itself as described above, is free from loss in driving force transmission efficiency during the driving operation, yet high in responsivity and moreover free from possibilities of malfunction. Furthermore, there is no room that such heat generation or noise as has mattered to the prior art example may occur.
In the above-described constitution, the turret type tool post may further comprise locking means for locking rotation of the piston, where the piston has an engaging portion formed therein, the engaging portion serving for, when the piston moves to the other side of the axial direction, engaging with the second drive shaft to hold the second drive shaft non-rotatable.
In this turret type tool post, the piston is locked by the locking means so as to be non-rotatable, and further when the piston is moved to the other side of the axial direction, releasing the engagement between the switching shaft and the second drive shaft, the engaging portion formed in the piston engages with the second drive shaft, holding the second drive shaft non-rotatable. As a result, it becomes implementable to prevent the second drive shaft or the tool held on the tool holder from idly rotating when the engagement between the switching shaft and the second drive shaft is released, and further to securely insert the second drive shaft into the switching shaft, and engage the same therewith, when the piston and the switching shaft are moved to the one side of the axial direction so that the second drive shaft is inserted again into the switching shaft.